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Ankur Mhatre 86246dc860 Three new article modules: configuration binding, profiles and config data, Spring AOP

configuration-properties/  @ConfigurationProperties vs @Value on Spring Boot 4.1.1.
  The relaxed-binding matrix is generated by binding each spelling rather than
  transcribed, and re-checked against real processes -- the in-process probe was
  wrong twice before it was right. Records the three findings that came out of it:
  @Value does get relaxed resolution inside Spring Boot (Boot attaches
  ConfigurationPropertySources), the configuration processor silently stops
  generating metadata on JDK 23+ when declared as a plain dependency, and @Valid is
  not what makes nested constraints run.

profiles-and-config/       Precedence, profiles, spring.config.import and config trees.
  /precedence reports every source holding a property in rank order with file and
  line, which turns "my profile file had no effect" into a two-line answer. Also
  pins the counterintuitive one: an imported file outranks the file that imported it.

spring-aop/                Designators, proxy types, and aspects that do not fire.
  One advice per supported designator so the reference table is generated from real
  matches; all fourteen unsupported designators fed to the parser. Two corrections to
  the reference documentation: unsupported designators throw
  UnsupportedPointcutPrimitiveException (extends RuntimeException, not
  IllegalArgumentException), and spring-boot-starter-aop was renamed to
  spring-boot-starter-aspectj in Boot 4.

19 contract tests across the three modules, 15 captured transcripts, all regenerated
by scripts/run-all.sh. Verified on Spring Boot 4.1.1, Spring Framework 7.0.9,
JDK 25.0.4.1.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Gip4srpzMwjgoba6uEfbr5

2026-09-08 16:47:48 +00:00

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@ConfigurationProperties vs @Value

Companion project for @ConfigurationProperties vs @Value in Spring Boot 4 on ankurm.com.

Every table and transcript quoted in that article was produced by running something here. Three of them were produced twice, because the first answer was wrong — see chapter 2.

Versions


Spring Boot	4.1.1
Spring Framework	7.0.9
JDK	Eclipse Temurin 25.0.4.1 (LTS)
Validation	Hibernate Validator via `spring-boot-starter-validation`

Quickstart

export JAVA_HOME=/path/to/jdk-25
mvn -DskipTests package
./scripts/run-all.sh          # regenerate every transcript in docs/output/
mvn test                      # 7 contract tests

Profiles

Profile	What it does
(none)	binds `demo.*` from `application.yaml`
`probe`	runs the relaxed-binding matrix and exits
`envprobe`	reports one property as seen by the binder and by `@Value`
`badvalidation`	values that violate every constraint, so startup fails
`csvlist`	the recipients list as a comma-separated string

Endpoints

Endpoint	Purpose
`GET /diag/bound`	the bound objects, and the same values via `@Value`
`GET /diag/origin?name=`	every source holding a property, in precedence order, with file and line

Both are diagnostics. Delete them before shipping.

Documentation

Captured output

File	Produced by
`00-versions.txt`	`scripts/demo-versions.sh`
`01-relaxed-matrix.txt`	`scripts/demo-relaxed-matrix.sh`
`02-env-var-binding.txt`	`scripts/demo-env-binding.sh`
`03-value-vs-binding.txt`	`scripts/demo-value-vs-binding.sh`
`04-validation-failure.txt`	`scripts/demo-validation.sh`
`05-metadata-generation.txt`	`scripts/demo-metadata-generation.sh`

Three findings worth the trip

@Value gets relaxed binding inside Spring Boot. The universal claim that it does not is a statement about the Spring Framework; Boot attaches a property source that changes it.
The configuration processor silently stops on JDK 23+ when declared as a plain dependency, so IDE auto-completion quietly dies while the build stays green.
@Valid is not what makes nested constraints run. Boot's ValidationBindHandler validates every object it binds.

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